Resonant reactively operating variable position transducer



W. T. HARRIS Jan. 23, 1962 RESONANT REACTIVELY OPERATING VARIABLE POSITION. TRANSDUCER Filed Nov. 7, 1955 2.57/4 Iii l-. k-u............-.-.

INVENTOR W/4Bw? I AAPP/s ATTO R N EYS 3,018,467 RESGNANT REACTIVELY GPERATING VARIABLE POSITIGN TRANSDUCER Wilbur '1. Harris, Siouthbury, Conn., assignor to The Harris Transducer Corporation, Woodhury, Conn, a

corporation of Connecticut Filed Nov. 7, 1955, Ser. No. 545,306 15 Claims. (Cl. 346-12) My invention relates to an electroacoustic-transducer construction of what I have termed the variable-position variety. Thus, the present type of transducer is related to other types disclosed and described in my US. Patents 2,713,127 and 2,756,405, issued July 12, 1955, and July 24, 1956, respectively, and in my US. Patent No. 2,822,- 482, issued June 5, 1957.

It is an object of the invention to provide improved transducer constructions of the character indicated.

It is another object to provide an improved variableposition transducer construction equally applicable to projection or reception of sound energy transmitted in water or through the earth.

It is specifically an object to provide a variable-position transducer with electrodynamic driving means.

It is a general object to meet the above objects with a construction well adapted to small low-frequency applications and to use in multiple-element array assemblies, for projecting moderate amounts of sonic power in water.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention;

FIG. 2 is a view similar to FIG. 1, but of an alternative embodiment, the embodiment of FIG. 2 being provided with a covering and mounting means which could be employed with the embodiment of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view, on an enlarged scale, showing one form of construction which could be used at the pole face gaps of the embodiments of either FIG. 1 or 2 in order to reduce eddy-current losses;

FIG. 4 is a view similar to FIG. 3 but showing specifically different structure for the reduction of eddy-current losses; and

FIG. 5 is a three-quarter perspective view of a part used in the construction of FIG. 4.

Briefly stated, my invention contemplates a simplified variable-position transducer construction, wherein simplification is achievable by elimination of the need for laminations, through provision of the reacting parts as separately fabricated and later assembled parts. Preferably, the construction involves concentric armature and stator masses of ferromagnetic material so formed with respect to each other as to define a generally toroidal flux path, through two longitudinally spaced annular gaps, and through both masses. Stiff spring means of non-magnetic material connect corresponding ends of the two masses, so as to permit bodily oscillation of the two masses on the longitudinal axis by reason of compliant connection through the non-magnetic spring members. Electrodynamic coil means is carried by one of the compliancecoupled masses in one or both of the gaps defined between these masses. In the two separate forms to be described, operation with and without permanently magnetized parts is contemplated.

Referring to FIG. 1 of the drawings, my invention is shown in application to a variable-position transducer comprising an elongated cylindrical armature mass 10,

concentrically disposed within a similarly elongated annular stator mass 11. Both masses Ill-11 are of ferromagnetic material (e.g. soft iron) and are so formed as to define, at their respective longitudinal ends, separate annular magnetic gaps 12-13. In the form shown, the gaps 12-13 are defined by separate pole-piece members 14-15, forming part of the stator mass 11 and connected to a central tubular body section 16. For compliant connection of the two masses Ill-11,1 provide separate spring members 17-18 at the respective longitudinal ends of the device; members 17-18 connect corresponding ends of the masses 10-11 in a manner to permit longitudinal relative oscillating movement of the two masses. In the form shown, the members 17-18 are spring diaphragms of non-magnetic material.

To complete the mechanical structure, protection of the diaphragms 17-18 and additional mass for the stator 11 are achieved by provision of massive end caps or bells 20-21. Tie bolts 22 are countersunk in the end bells 20-21 and serve to secure all stator parts together. Bolts 23 secure the ends of the armature mass 10 to the spring diaphragms 17-18. For underwater applications, a plurality of so-called O-ring seals 24-25-26 (coaxial with the armature and stator) are compressed upon takeup of the bolts 22, so as to assure against leakage to the inner parts of the assembly.

The parts thus far described permit establishment of a toroidal flux path, illustrated schematically by oval lines 27 in the drawing; this path may be polarized, for example, in the direction to pass longitudinally right to left through body 16, radially inward through pole piece 14 and across the gap 12, longitudinally left to right through the armature 10, radially outwardly across the gap 13 and through pole piece 15, and back to the body 16. In the form shown in FIG. 1, polarizing flux is circulated by excitation of a polarizing winding 29 carried in the annular space between pole pieces and smoothly retained in place by a non-magnetic sheath 30; to reduce windage, sheath 30 preferably has a bore diameter matching the bore diameter of pole pieces 14-15. A.C. or signal-winding means is of the electrodynamic variety and is therefore located in one or both gaps 12-13; in the form shown, such winding means is bonded directly to the armature 10. I prefer that the signal-winding means shall comprise separate windings 31-32 and located in the gaps 12-13, respectively. Because flux in the path .27 will at any instant be circulating in opposite radial directions through the respective gaps, it is necessary that the windings 31-32 be applied to armature 10 in opposed sense, so that they may be connected in series to an A.C. or signal source, and so that the mechanical forces they develop will be additive. Leads to the various windings are shown brought through insulated bushings, as at 33, in one of the diaphragms (17) and through suitable gland means 34 in the adjacent end bell 20.

On application of polarizing current to the winding 29 and of an A.C. signal to the windings 31-32, forces will be developed causing relative longitudinal displace ment of the two masses 10-11. The compliant connection at 17-18 between these masses assures development of powerful oscillations at and near the mechanicalresonance frequency of the structure, and the outer body, including the mass 11 and end bells 26-21, will reactively oscillate with respect to armature 10, with bodily motion along the longitudinal axis. By this means, an eflicient transfer of power may be achieved to the fluid, ground, or other medium in which the transducer is immersed. For receiving purposes, the windings 31-32 will develop adequate signals in response to longitudinal displacement of the outer body or stator mass 11-20- \21, as will be understood.

In FIG. 2, I illustrate a construction closely resem- Patented Jan. 23, 1962' bling that of FIG. 1 and, therefore, corresponding parts have been given the same reference numerals. In the arrangement of FIG. 2, one of the two masses includes a permanently polarized member as, for example, the tubular body member 16; member 16' may be a permanent magnet, with the opposite poles at the longitudinal ends thereof. The members 16' may thus be fabricated of a material such as that known to the trade as Alnico, while the other ferromagnetic parts, such as pole pieces 14-15 and armature 10 may be fabricated of soft iron. A.-'C. or signal leads are brought through the gland 34. Operation of the device of FIG. 2 will be essentially the same as that described for FIG. 1, except of course that no polarizing current is necessary.

FIG. 2 further illustrates mounting means suitable for transducers of the character indicated. Such mounting means should be longitudinally yieldable, and in the form shown, comprises a single peripherally continuous annular ring 35 of rubber-like material, bonded to the stator and projecting radially outwardly from a location longitudinally symmetrical with respect to the ends of the device. The transducer of FIG. 2 happens to be fully jacketed by a boot 36 of sound-transmitting rubber-like material, intimately bonded to all exposed parts of the device; it is thus convenient to provide the mounting flange 35 as an integral part of said boot 36. Mounting holes 37 may be provided in the flange 35 with individual molded reinforcement means 38, all as described in greater detail in my copending patent application Serial No. 454,712, filed September 8, 1954, now Patent No. 2,947,969.

The constructions of FIGS. 1 and 2 will be understood as representative of general organizations of parts. Actually, with an all-iron construction of all structural parts of the magnetic path, the eificiency of the device is im paired, inasmuch as movement of the armature with the driver winding will induce eddy currents in the surface of the iron armature just underneath the driver winding. In FIGS. 3 to 5, I illustrate two alternatives for substantially'eliminating this'source of efficiency loss.

Since the two driver windings 31-32 are balanced and in opposition, there is no net A.-C. flux in the armature, and treatment to reduce eddy-current losses can be localized, i.e. limited substantially to the troublesome region immediately underneath or within the driverwinding coils 3132.

In FIG. 3, I illustrate one means of locally reducing eddy-current losses, by employing a separate ferrite-ring insert 40 in the armature 10, immediately underneath each winding 32 (and 31, not shown); ring 40 may be bonded to and form part of armature 10. Since the saturation flux density of ferrites is much lower than that of iron, the pole pieces 14-15 should be of greater proportional axial extent than shown in FIGS. 1 and 2, and each ferrite ring 40 and associated windings 32 (and 31, not shown) should be of substantially corresponding greater axial extent.

FIGS. 4 and illustrate the further alternative in which surface portions of the armature are laminated beneath each of the windings 32 (and 31, not shown). It thin iron washer-type plastic-bonded laminations are used, the high permeability and high saturation-flux density of the iron magnetic circuit can be preserved at the critical region, so that axial proportions of pole pieces 14-15 may be generally as shown in FIGS. 1 and 2; in fact, some gain can be realized, by using high-cobalt alloy laminations, if desired. However, the mere use of simple fiat washer-type laminations is not preferred, because laminations in the axial direction are needed for best results. In FIGS. 4 and 5, I effectively accomplish this result, by laminating with washers 42 having radially sheared cuts 43 around the periphery, as best shown in FIG. 5. In FIG. 5, the cuts 43 are shown to form alternately displaced radial lugs 44-45, because this is how the blanking and shearing tool actually makes the pieces in one automatic punch-press operation. Actually, the tools shear the serrations as illustrated, with alternately displaced lugs, but then restore the washer 42 to its flat form, leaving radial fissures at 43. On annealing, these fissures 43 provide high resistance to eddy currents, and a bonded stacked assembly of washers 42 is readily developed, as shown in FIG. 4.

It will be appreciated that I have described .a relatively simple variable-position transducer construction, applicable for the purposes indicated. The basic .simplicity of the construction makes for low-cost assembly, and the construction happens to be ideally suited to lowfrequency underwater sound-projection and to sound projection in earth, as for geophysical-prospecting applications.

While I have described the invention in detail for the preferred forms illustrated, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

1. A mechanically resonant two-way-acting electroacoustic transducer, comprising an elongated cylindrical ferromagnetic armature mass, an elongated annular ferromagnetic SL! mass surrounding said armature mass and substantially coextensive therewith, one of said masses including at each of the longitudinal ends thereof a radially extending pole piece extending into close clearance relation with the other of said members, whereby an annular magnetic gap is defined at each of said ends, so that a generally toroidal flux path may be established through both gaps and both masses, separate nonmagnetic resilient disc diaphragms reactively connecting the corresponding longitudinal ends of said masses to each other for axial reactively coupled resonant oscillation of said masses, said diaphragms being the only means connecting said masses, and electrodynamic-coil means carried by one of said masses in one of said gaps for exciting said masses in mutually reactive resonant relative longitudinal oscillation.

.2. A transducer according to claim 1, in which said stator includes a peripherally continuous cover'of rubberlike material, bonded to the outer surfaces of said stator mass and including outwardly projecting mounting means integral with said cover and yieldable along the axis of said transducer.

3. A transducer according to claim 1, in which said transducer includes a circumferentially extending radially projecting mounting ring of yieldable material bonded to said stator mass substantially symmetrically between the longitudinal ends of said transducer.

4. A -mechanically resonant two-way-acting electroacoustic transducer, comp-rising an elongated cylindrical ferromagnetic armature mass, an elongated annular ferromagnetic stator mass surrounding said armature mass and substantially coextensive therewith, said stator mass including at each of the longitudinal ends thereof radially inwardly projecting circumferentially continuous portions projecting into close clearance relation with said armature mass and defining magnetic gaps at the locations of close clearance relation, whereby a generally toroidal flux path may be established through both gaps and both masses, separate non-magnetic spring members reactively connecting the corresponding longitudinal ends of said masses to each other for axially reactively coupled resonant longitudinal oscillation of said masses, and electrodynamic-coil means carried by one of said masses in one of said gaps for exciting said masses in mutually reactive resonant relative longitudinal oscillation.

5. A mechanically resonant two-way-acting electroacoustic transducer, comprising an elongated cylindrical ferromagnetic armature mass; an elongated annular ferromagnetic stator mass surrounding said armature mass; one of said masses including, radially opposite each of the ef ,fective longitudinal ends of the other of said masses, a pole piece defining an annular magnetic gap at each of said ends, one of said masses including a permanently magnetized portion, whereby a generally toroidal flux path is defined through both gaps and both masses; separate nonmagnetic spring members yieldably securing the corresponding longitudinal ends of said masses to each other for axially reactively coupled resonant longitudinal oscillation of said masses; and electrodynamic-coil means carried by one of said masses in one of said gaps for exciting said masses in mutually reactive resonant relative longitudinal oscillation.

6. A mechanically resonant two-way-acting electroacoustic transducer, comprising a rigid elongated cylindrical ferromagnetic armature mass; a rigid elongated annular ferromagnetic stator mass surrounding said armature rnass; one of said masses including, radially opposite each of the eifective longitudinal ends of the other of said masses, a pole piece defining an annular magnetic gap at each of said ends, whereby a generally toroidal flux path is defined through both gaps and both masses; separate non-magnetic spring members yieldably securing the corresponding longitudinal ends of said masses to each other for axially reactively coupled resonant longitudinal oscillation of said masses; separate rigid end caps for the respective longitudinal ends of said transducer, said end caps being peripherally secured to said stator mass and being in axial end-clearance relation with the axial ends of said armature mass, whereby said stator mass and end caps fully surrounded said armature mass; and electrodynamic-coil means carried by one of said masses in one of said gaps for exciting said masses in mutually reactive resonant relative longitudinal oscillation.

7. A mechanically resonant two-way-acting electroacoustic transducer, comprising an elongated cylindrical ferromagnetic armature mass; an elongated annular ferromagnetic stator mass surrounding said armature mass; one of said masses including, radially opposite each of the efiective longitudinal ends of the other of said masses, a pole piece defining an annular magnetic gap at each of said ends, polarizing-winding means carried by one of said masses at a location longitudinally between said gaps, whereby a generally toroidal flux path is defined through both gaps and both masses; separate non-magnetic spring members yieldably securing the corresponding longitudinal ends of said masses to each other for axially reactively coupled resonant longitudinal oscillation of said masses; and electrodynamic-coil means carried by one of said masses in one of said gaps for exciting said masses in mutually reactive resonant relative longitudinal oscillation.

8. An electroacoustic transducer, comprising an elongated cylindrical ferromagnetic armature mass, an elongated annular ferromagnetic stator mass surrounding said armature mass and substantially coextensive therewith, one of said masses including at each of the longitudinal ends thereof a pole piece defining with the other of said masses an annular magnetic gap at each of said ends, whereby a generally toroidal flux path is defined through both gaps and both masses, non-magnetic spring means yieldably securing said masses to each other for compliance-coupled relative longitudinal oscillation of said masses, and electrodynamic coil means carried by one of said masses in both said gaps, said armature mass including eddy-current-resisting ferromagnetic means in the region immediately within said coil means.

9. A transducer according to claim 8, in which said last defined means is a ferrite.

10. A transducer according to claim 8, in which said last-defined means includes a laminated stack of washers.

11. A transducer according to claim 10, in which said washers are each generally radially slitted to define effectively longitudinal laminations,

12. A transducer according to claim 8, in which said last-defined means is an inserted ring carried directly by the rest of said armature mass.

13. A transducer according to claim 12, in which said rest of said armature mass is a single piece of iron.

14. An electroacoustic transducer, comprising an elongated cylindrical ferromagnetic armature mass, an elongated annular ferromagnetic stator mass surrounding said armature mass and substantially coextensive therewith, one of said masses including at each of the longitudinal ends thereof a pole piece defining with the other of said masses an annular magnetic gap at each of said ends, whereby a generally toroidal flux path is defined through both gaps and both masses, non-magnetic spring means yieldably securing said masses to each other for compliance-coupled relative longitudinal oscillation of said masses, and electrodynamic coil means carried by one of said masses in both said gaps, said one mass including eddy-current-resisting ferromagnetic means in the region immediately adjacent said coil means.

15. An electroacoustic transducer, comprising an elongated cylindrical ferromagnetic armature mass, an elongated annular ferromagnetic stator mass surrounding said armature mass and substantially coextensive therewith, one of said masses including at each of the longitudinal ends thereof a pole piece defining with the other of said masses an annular magnetic gap at each of said ends, whereby a generally toroidal flux path is defined through both gaps and both masses, non-magnetic spring means yieldably securing said masses to each other for compliance-coupled relative longitudinal oscillation of said masses, and electrodynamic coil means carried by one of said masses in one of said gaps, said one mass including eddy-current-resisting ferromagnetic means in the region immediately adjacent said coil means.

References Cited in the file of this patent UNITED STATES PATENTS 1,333,298 Evershed et a1. Mar. 9, 1920 1,582,590 Fay Apr. 27, 1926 1,984,383 Russell Dec. 18, 1934 2,271,667 Sproule Feb. 3, 1942 2,348,225 Petty May 9, 1944 2,410,805 Black Nov. 12, 1946 2,424,549 Black et al. July 29, 1947 2,740,946 Geneslay Apr. 3, 1956 2,768,364 Camp Oct. 23, 1956 2,776,560 Erath et a1. Jan. 8, 1957 

1. A MECHANICALLY RESONANT TWO-WAY-ACTING ELECTROACOUSTIC TRANSDUCER, COMPRISING AN ELONGATED CYLINDRICAL FEROMAGNETIC ARMATURE MASS, AN ELONGATED ANNULAR FERROMAGNETIC STATOR MASS SURROUNGING SAID ARMATURE MASS AND SUSBTANTIALLY COEXTENSIVE THEREWITH, ONE OF SAID MASSES INCLUDING AT EACH OF THE LONGITUDIANAL ENDS THEREOF A RADIALLY EXTENDING POLE PIECE EXTENDING INTO CLOSE CLEARANCE RELATION WITH THE OTHER OF SIAD MEMBERS, WHEREBY AN ANNULAR MAGNETIC GAP IS DEFINED AT EACH OF SAID ENDS, SO THAT A GENERALLY TOROIDAL FLUX PATH MAY BE ESTABLISHED THROUGH BOTH GAPS AND BOTH MASSES, SEPARATE NONMAGNETIC RESILIENT DISC DIAPHRAGMS REACTIVITY CONNECTING THE CORRESPONDING LONGITUDINAL ENDS OF SAID MASSES TO 